P2494: Low EGR bypass feedback is different from a closed valve

P2494 identifies low electrical feedback from the high-pressure EGR cooler-bypass position sensor in the cited GM system. The monitor evaluates raw analog voltage as a percentage of the 5 V reference. It is not simply saying that the valve has reached its closed mechanical position.

Establish whether the feedback remains in range

The low threshold is below 1% of the reference. The neighboring high-range monitor, P2495, uses the opposite end of that scale. This distinction matters when a scan tool also displays a calculated valve percentage: a converted position value can conceal that the underlying electrical signal is outside its valid range.

Monitoring must be enabled by calibration, cranking must have ended, and the powertrain-relay supply must exceed 11 V. A signal observed during cranking or inadequate supply does not reproduce this particular running check.

Use the sample history, not one snapshot

GM specifies 200 failed observations out of 250 samples and a 6.25 ms function task. The sample decision and two-trip reporting describe different levels of fault confirmation. Do not interpret the trip count as a sensor-response time.

For verification, retain the raw feedback, reference context and supply state together. If the feedback is electrically invalid, a mechanical-position conclusion should wait until the signal can be interpreted reliably. The table does not locate a grounded wire or establish that the sensor itself requires replacement.

Source and applicability

2025 GM 25OBDG04A documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred. These criteria explain controller logic, not a complete repair procedure. 25OBDG04A, PDF page 1208. 25OBDG04A, PDF page 1209.